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Histogenesis of Irreversible Changes in the Female Genital Tract After Perinatal Exposure to Hormones and Related Substances
Published in Takao Mori, Hiroshi Nagasawa, Toxicity of Hormones in Perinatal Life, 2020
Morphogenetic effects are just one example of the different effects produced by steroids. The insect steroid hormone ecdysone is of importance for metamorphosis. During normal sexual differentiation in mammals, exposure of the genital primordia to testicular androgen allows expression of the male genotype into a male phenotype. Estrogens do not seem to have a similar morphogenetic effect on the female genotype. It is well documented that by exposing immature males to exogenous estrogens or females to androgens, the normal sexual phenotype can be influenced.
Evidence for a Thymus-Pineal Axis
Published in Nate F. Cardarelli, The Thymus in Health and Senescence, 2019
Ecdysone is involved in larval, pupal, and imaginal molts, and is active in all orders of insects studied.190 (Oddly enough, it is also present in some plants, such as ferns.191) To induce molting, ecdysone quickly accumulates to a given level in the hemolymph.192 Initiation of molting activity requires a quick burst of hormone.193 Elimination must also be rapid or a new molting cycle could be initiated too rapidly following the old.194
Tin and The Aging Process
Published in Nate F. Cardarelli, Tin as a Vital Nutrient:, 2019
Ecdysone was isolated from silkworm (Bombyx) pupae in 1954 and recognized as a molting hormone.16 A year or so later another ecdysone (now called β-ecdysone) was isolated.17 Activity was noted upon oral ingestion and the degree of response for a given dosage was species dependent.18 Crustecydsone, the molting hormone of crustaceans, was isolated and identified19 and found to be identical to β-ecdysone (20-hyroxyecdysone).20 After recognition of its steroid character it has been termed “ecdyster-one”.20 There is some degree of controversy as to whether ecdysone is synthesized in the ecdysial glands, or elsewhere through mediation of enzymes etc. secreted by this gland.21 In any event, ecdysone is synthesized from exogenous cholesterol,13,22 penetrates target cell membranes, and through radioautography, is found within the nucleus.23 It acts on DNA to stimulate specific mRNA production.24–26 The basic target is cells of the larval epidermis.27
Inter-organ regulation by the brain in Drosophila development and physiology
Published in Journal of Neurogenetics, 2023
Sunggyu Yoon, Mingyu Shin, Jiwon Shim
As growth and metabolism are coupled, metamorphosis, driven by ecdysone secretion in the prothoracic gland, is closely associated with the insulin pathway. Ilp2, Ilp3, and Ilp5 from IPC activate the insulin receptor in the prothoracic gland and trigger downstream targets through PI3K/AKT and FOXO. Upon activating InR in the prothoracic gland, transcription of Halloween genes is inhibited, and ecdysone secretion is eventually reduced (Koyama et al., 2014; Mirth et al., 2005), showing an antagonistic correlation between insulin and ecdysone. Conversely, when a larva exceeds the critical weight and the blood insulin concentration falls, ecdysone secretion rises with a large pulse (Kannangara et al., 2021). In starved larvae, blood insulin levels drop and Foxo forms a complex with usp (ultraspiracle), inhibiting ecdysone gene expression and delaying metamorphosis (Koyama et al., 2014). Altogether, these findings provide insights into the intricate and tightly regulated interactions between the brain and other organs during developmental processes that allow animals to grow within controlled time frames and size parameters (Table 3).
A review of the evidence for endocrine disrupting effects of current-use chemicals on wildlife populations
Published in Critical Reviews in Toxicology, 2018
Peter Matthiessen, James R. Wheeler, Lennart Weltje
Another weak case, perhaps again due to lack of data, concerns so-called estrogenic and other effects in mollusks and crustaceans. There is no doubt that exposure to estrogenic effluents causes elevations of ALP in some mollusks, but the mode of action is unknown (it may not even be ED), and there is no evidence for resulting adverse apical effects at the population level. There is weak experimental evidence that estrogen exposure in bivalves can cause reproductive damage, and only limited field evidence of this. Surprisingly, there is also no hard evidence for the adverse effects of ecdysone- and juvenile-hormone active insecticides on non-target insects and crustaceans, although this is not necessarily evidence of absence. More research in this field would be desirable.
Specific and combined effects of dietary ethanol and arginine on Drosophila melanogaster
Published in Drug and Chemical Toxicology, 2023
Maria M. Bayliak, Oleh I. Demianchuk, Dmytro V. Gospodaryov, Vitalii A. Balatskyi, Volodymyr I. Lushchak
It was found that G6PDH expression in Drosophila is also regulated by estrogen related receptor (dERR) and transcription factor Mlx (Teesalu et al. 2017, Beebe et al. 2020). Nitric oxide might also be involved in down-regulation of G6PDH and different isoenzymes of GST, if fruit flies would have a regulator, similar to Bach1 protein in vertebrates. Bach1 was found to be responsive to •NO, at the same time being a negative regulator of some Nrf2 targets (Tsuneyoshi 2020). Among proteins of D. melanogaster, significant homology to Bach1 can be found for different isoforms of Cnc, which is also a homolog of Nrf2, and tramtrack protein, which controls development (Badenhorst et al. 2002, Sykiotis and Bohmann 2010). Interestingly, •NO might also act via dERR since •NO was found to regulate ecdysone biosynthesis (Texada et al. 2020). In turn, dERR and ecdysone receptor were found to operate in concert in the regulation of gene expression (Kovalenko et al. 2019). Indeed, •NO can exert concentration-dependent effects, being a promoter of development and important intracellular messenger at relatively low concentrations but a damaging substance at high ones. For example, the dependence of catalase, G6PDH, GST, and thioredoxin reductase activities in young adults of D. melanogaster on concentration of SNP, an •NO donor, had bell shape, unlike the activity of aconitase (Lozinsky et al. 2012). The decrease in G6PDH activity we observe in the current study (Figure 6(a)) can also be explained by its possible oxidation by free radicals, such as •NO and its derivatives like peroxynitrite. The homologous enzyme in the baker’s yeast Saccharomyces cerevisiae was found to be sensitive to free radical oxidation (Gospodaryov et al. 2005).